Telechelic polymers can be simply defined as polymers that bear reactive functional groups at their chain termini. The interest in these polymeric materials is derived from the fact that through these reactive end groups, a vast number of macromolecular materials can be prepared. Telechelic polymers have found application in the synthesis of block copolymers, star polymers, crosslinked polymer networks, and ionic polymer networks. Low molecular weight liquid telechelic polymers have been successfully used in reaction injection molding, and the formation of ABA triblock and multiblock copolymers via telechelic polymers has dramatically impacted the development of thermoplastic elastomers. Based on these numerous valuable applications, considerable research efforts have been devoted to improving the synthesis of telechelic polymers.
The development of telechelic polymers with crosslinkable end groups such as methacrylate or epoxide groups is of interest for the preparation of interpenetrating polymer networks, AB crosslinked polymeric materials, more thermally and chemically resistant materials, and for the immobilization of biomaterials. However, these reactive end groups have been typically incorporated through a post-polymerization transformation due to the instability of these functional groups to tolerate many of the typical conditions associated with polymerization reactions.
Recently, a non-metathesis-mediated polymer degradation approach was applied to polymers derived from ROMP. Copolymerization of cyclooctadiene (“COD”) with either cis-4,7-dihydro-1,3-dioxepan (1) or cis-4,7-dihydro-2-phenyl-1,3-dioxepan (2) using well-defined ruthenium-based metathesis initiators, (PCY3)Cl2Ru═CHR′ (wherein R′═Ph (3), or wherein R′═(CH═CPh2) (4)), resulted in a polymer bearing both poly(butadiene) and acetal units along the backbone. Subsequent acid hydrolysis of these acetal units resulted in the desired hydroxytelechelic poly(butadiene) (“HTPBD”) oligomers in moderate yields. Although this method proved to be successful for the synthesis of HTPBD, this method is not generally applicable for the preparation of telechelic polymers with other functional end groups.
As a result, a need exists for methods for synthesizing telechelic polymers having a variety of end groups, particularly crosslinkable end groups and which do not require post-polymerization transformations for polymer functionalization.